SHORTLY AFTER the September 11th, 2001, terrorist attacks, I differed with a friend who said I was wrong to support an invasion of Afghanistan to root out al-Qaeda and punish the Taliban. I said the United States had no choice but to make the terrorists and their Afghan hosts pay for what they had done. I insisted I was right. That, amazingly, was almost 16 years ago. I never expected to be right for so long.

Afghanistan has become the war without end. The United States cannot win it and cannot afford to lose it. The country consumes American wealth and lives. More than 2,300 American soldiers have died there. Some $828 billion has been spent there. Generals who once commanded there are deep into their retirement, and soldiers who fought there as youths are approaching middle age. Kipling's Brits could not control the country; neither could the Russians nor, come to think of it, can the Afghans. Afghanistan is not a country. It's a chronic disease.

The Trump administration, like the several that preceded it — George W. Bush twice and Barack Obama twice — is mulling a new approach. This time, there will be no certain date when American involvement will end — a bit of Obama-era silliness that, in effect, told the Taliban to hold on, be patient, and the Yanks will leave. President Trump has reportedly left decisions on troop levels to Defense Secretary Jim Mattis, a retired Marine general and a man of such reckless courage that he refused to fawn over Trump at a Cabinet meeting. Somewhere a medal awaits.

Mattis, however, is reportedly cool to a plan developed by Erik Prince that would entail turning over a substantial part of the Afghanistan effort to “contracted European professional soldiers” — what you and I call mercenaries. The term has an odious connotation, but there is no avoiding it. Prince is referring to British, French, Spanish and other Europeans who are experienced soldiers. They would not, as is now the case with Americans, be rotated out of the country after a period of time to the effect that, in a sense, the United States is always starting anew. These contract soldiers would get about $600 a day to command Afghan troops and be embedded with them — much as U.S. Special Operations forces now are. Trouble is, the United States has a limited number of those forces.

I took the phrase “contracted European professional soldiers” from an op-ed Prince wrote for The Wall Street Journal. It seems the president read it and was intrigued. Good. The plan has its virtues, the most obvious one being that nothing else has worked — and more of the same is going to produce more of the same. The plan also has its difficulties, one of them being its provenance. Prince is the founder of the highly controversial security firm Blackwater, which he has since sold. While he owned it, though, some of its employees opened fire in Baghdad's Nisour Square, killing 17 civilians and wounding more than 20.

If Prince remains controversial, he also remains influential. He's a former Navy SEAL who has entry to the White House and the CIA, and his sister is Betsy DeVos, the education secretary. Like his sister, Prince is rich and indefatigable. He has been peddling his Afghanistan plan for more than a year, and while it is frequently described with the pejorative term “for profit”, it has, as Prince contends, a pedigree. “Contract Europeans” were used by the British East India Company to rule India for more than 100 years.

Prince's references to colonial rule are admiring. He has even revived the term “viceroy” to describe the person who would direct American policy in Afghanistan. By his count, the United States has had 17 military commanders in the past 15 years — not counting ambassadors, CIA station chiefs and, of course, the inevitable special representatives, such as Richard Holbrooke, whose genius and energy were wasted by Obama. All that would stop. The viceroy would run things.

The war in Afghanistan is the longest in American history. A loss would allow the country to revert to a terrorist haven. A win would require a commitment in manpower that the United States is not willing to make. In almost 16 years, the fight in Afghanistan has gone from noble cause to onerous obligation. I don't know if Prince has the answer, but he has come up with one way to sustain the fight at less cost in American lives and treasure. Will it work? I don't know, but nothing else has.

• Richard Cohen writes a weekly political column for The Washington Post.